(1) Field of the Invention
The present invention relates to image resolution. More particularly, the present invention relates to methods and systems to determine the resolution of a sonar image.
(2) Description of the Prior Art
Sonar image resolution and concomitant image quality are difficult to determine in field conditions. While there are relationships that can predict the theoretical limit of range and cross-range resolution, theoretical limits are rarely achieved in practice. In an attempt to measure achieved resolution, one often uses some target and evaluates the response of the target to determine the 3 dB down width of the point object response. This exercise is difficult in that the targets are often larger than the intended resolution and difficult to image at the desired range and aspect due to localization errors experienced in underwater navigation.
Future synthetic aperture sonar (SAS) systems will need to operate in shallow water littoral environments. Very shallow water environments are known to have low ping-to-ping correlation and elevated levels of system motion. Current generation motion estimation techniques are not reliable in low correlation environments when system motion is high.
Thus, a need has been recognized in the state of the art to develop innovative techniques in order to quantify the fidelity of SAS imagery.